Thermoplastic sealed-sheath covering upon electrical bus-bar conductors

ABSTRACT

An improved and relatively inexpensive electrical conductor, such as a bus-bar, or feeder conductor, of aluminum or copper, for example, is provided with a thermoplastic elongated tubular sheath, or sheath tubing, such as polyvinyl chloride heatreactive tubing of resinous material, having the ends of the sheath, or tubing, sealed, in a water-tight fashion to the busbar by a thermoplastic resinous tape material. In one method of the invention, the resinous tape may be wound adjacent the outer ends of the bus-bar at spaced areas thereon, and the thermoplastic tubing subsequently pulled, as a second operation, upon the bus-bar and heat shrunk into place over the aforesaid spaced taped areas. Another alternate method for sealing the thermoplastic sheath tubing to the bus-bar, is to heat-shrink the thermoplastic insulating tubing, or &#39;&#39;&#39;&#39;boot&#39;&#39;&#39;&#39; upon the bus-bar after pulling it into place, scalp excess tubing to a specified dimension upon the bus-bar, and then band or tape each of the scalped ends of the tubing, or &#39;&#39;&#39;&#39;boot&#39;&#39;&#39;&#39; with a suitable thermoplastic resinous tape material, such, for example, as polyvinyl chloride adhesive tape.

United States Patent 1191 Toth et al.

1451 Aug. 28, 1973 [75] Inventors: Julius Toth, Beaver; Edward M.

Walker, Industry, both of Pa.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Sept. 15, 1971 [21] Appl. No.: 180,872

Related US. Application Data [63] Continuation of Ser. No. 888,296, Dec.29, 1969,

abandoned.

[52] US. Cl.... 174/120 SR, 174/016. 8, 174/110 R [51]' Int. Cl. 1101b7/02 [58] Field of Search 174/110 R, DIG. 8,

174/68 B, 120 R, 120 SR; 117/114 R, 48, 66

[56] References Cited UNITED STATES PATENTS 6/1883 Steward 174/110RH1936 Currie 174/D1G. 8

OTHER PUBLICATIONS Alphlex Shrinkable Tubing Ad. Brochure, pg. l-2.

Primary Examiner-E. A. Goldberg Attorney- A. T. Stratton, W. R. Crout etal.

[ 5 7] ABSTRACT An improved and relatively inexpensive electricalconductor, such as a bus-bar, or feeder conductor, of aluminum orcopper, for example, is provided with a thermoplastic elongated tubularsheath, or sheath tubing, such as polyvinyl chloride heat-reactivetubing of resinous material, having the ends of the sheath, or tubing,sealed, in a water-tight fashion to the bus-bar by a thermoplasticresinous tape material. In one method of the invention, the resinoustape may be wound adjacent the outer ends of the bus-bar at spaced areasthereon, and the thermoplastic tubing subsequently pulled, as a secondoperation, upon the bus-bar and heat shrunk into place over theaforesaid spaced taped areas.

Another alternate method for sealing the thermoplastic sheath tubing tothe bus-bar, is to heat-shrink the thermoplastic insulating tubing, orboot" upon the bus-bar after pulling it into place, scalp excess tubing2'o43796 6/1936 Frank 174/68 B to a specified dimension upon thebus-bar, and then 3,086,888 4/1963 Stratton 174/110 R 3,345,455 10/1967Goody D I i 174/1) R band or tape each of the scalped ends of thetubing, or 3,417,176 12/1968 Anderson 174/1310. 8 with a Suitablethermoplastic resinous tape FOREIGN PATENTS OR APPLICATIONS 23?" exampleas pmyvmy' chlmde 883,155 11/1961 Great Britain l74/DIG. 8

5 Claims, 11 Drawing Figures 'POLY'VINYL CHLORIDE ADHESIVE-TAPE mm A TOPOVERLAY 01- "PLIOFILM" TRANSPARENT TAPE.

PAIENIEBmea ma SNEEI 1 0F 3 BUM? AFTER HEAT SHSRUNK INTO PLACESFIALPEDVI FIG.4B.

LSCALPED PATENTEI] M19 2 8 I975 6 m G G F F 2 IIIIJ I I ||.-|l Illlll DWu E H P L A C S K N U R H 3 E C E H O W N F A lll D r E P L A 1 C s u uA II I I l I I l I III l I I 2 I l I I l I. IDL .m I

POLYVINYL CHLORIDE ADHESIVE TAPE WITH A TOP OVERLAY OF "PLIOFILM"TRANSPARENT TAPE WITNESSES INVENTORS 4 Z Q L Julius Tofh a Edward MWalker jam 4% M BM ATTORNEY THERMOPLASTIC SEALED-SHEATH COVERING UPONELECTRICAL BUS-BAR CONDUCTORS CROSS-REFERENCES TO RELATED APPLICATIONSBACKGROUND OF THE INVENTION It has been customary in the past to windinsulating tape over bus-bars in switchgear applications. Reference maybe made to U.S. Pat. No. 3,042,890, issued July 3, 1962, D. H. Gamble etal., and to U.S. Pat. No. 2,946,034, issued July I9, 1960, Washburn. Thewinding of such insulating tape, or the use of insulating tubes over thebus-bars, insures thereby that a very high-dielectric-strengthinsulating material must be penetrated, before flashover to adjacentgrounded parts may ensue. Reference may be made to the insulating sleeve22 set forth in U.S. Pat. No. 2,865,980, issued Dec. 23, I958, Popovichet al., and to U.S. Pat. No. 2,653,991, issued Sept. 29, 1953, Dyer etal. with particular reference being directed to FIG. 6 of thelastmentioned patent. Consequently, the prior art has dictated thedesirability of using insulating material upon bus-bar conductors forassisting in withstanding the line-to-ground voltage.

Reference may be made to U.S. Pat. No. 3,347,975, issued Oct. 17, 1967to B. M. Shannon, and also to U.S. Pat. No. 3,I78,668 issued Apr. 13,1965 to C. L. Weimer et al., all showing an insulating covering. Inaddition, reference may be made to U.S. Pat. No. 3,148,3l2, issued Dec.8, I964 S. S. Fouse.

It is well known by those skilled in the art, in plating processes, thatis is customary to dip the bus-bar into several tank solutions, evenapproaching 12 in number. As a typical example, one of the tanksolutions will contain a cleaning solution, followed by other tankssequentially containing water rinse solution, a dilute nitric acidsolution, a water rinse, an immersion zinc solution, two separate waterrinse tanks, a copper plating solution, a water rinse solution, a silverplating solution, followed by two separate final water rinse tanks. As aresult, the number of tanks employed, in this instance, is 12 in'number.

As will be obvious, it is desirable for certain applica tions to limitthe extent or area of the silver-plating coating upon the bus-bar, sincesilver is a very expensive material costing roughly $25 .00 per pound.If the insulating tubing is allowed to have a loose fit upon thebus-bar, or electrical conductor, the solutions in the various tankswill tend to creep into the annular space between the interior of thetubing and the outer face of the bus-bar thereby causing undesirabledeformation and deterioration of the tubing, and also blistering, ordeterioration of the tubing. In addition, there is a loss of the platingsolutions and corrosive damage to the metallic bus-bar.

SUMMARY OF THE INVENTION In accordance with a preferred embodiment ofthe present invention, the extent or area of silver plating upon abus-bar, such as a copper or aluminum bus-bar, is limited by providing asealed water-tight and chemical-resistant sheath coating upon thebus-bar itself for a considerable portion of its length, and to therebylimit the silver electroplating to the end portions only of the bus-bar,where the bolted connections to other busbars, or adjoining connectorelements, may take place, as well known by those skilled in the art.

In accordance with preferred methods of the present invention, athermoplastic resinous material, such as a polyvinyl chloride adhesivetape is wound or taped upon the bus-bar at spaced locations adjacent itsends. The thermoplastic tubing, or boot is then positioned into place bypulling it on over the spaced taped portions, and it is then heat-shrunkupon the bus-bar, thereby creating a tight fit thereon. An alternatemethod for sealing the same tubing or thermoplastic sheath to thebus-bar, ends would be to heat-shrink the thermoplastic insulatingtubing upon the bus-bar, as a first operation, scalp, or trim excesstubing to a specified dimension, and then band each of the outer scalpedends of the boot" with the same polyvinyl chloride adhesive tape.

Further advantages may readily be perceived by those skilled in the artupon reading the following specification, taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view of a bus-bar priortothe process steps of the instant invention;

FIG. 2 is a side view of the bus-bar of FIG. 1;

FIG.. 3 illustrates the taping of the spaced adhesive bands to thebus-bar of FIG. 1 as spaced-apart locations;

FIG. 4 illustrates the positioning, or pulling of the thermoplasticpreformed tubing over the previously taped bus-bar to heat-shrink thesame into place;

FIG. 4A illustrates the tube after shrinking.

FIG. 4B illustrates the final "scalping" operation;

FIG. 5 illustrates the pulling of a preformed thermoplastic resinoustubing, or boot over the bus-bar;

FIG. 6 illustrates the scalping operation following the heat shrinkingof the thermoplastic boot over the bus-bar of FIG. 5; A

FIG. 7 illustrates the taping of the ends of the shrunk boot to form asecure adherence therebetween;

FIG. 8 illustrates the covering of the polyvinyl chloride adhesive tapewith a top overlay of Pliofilm transparent tape which facilitateshandling of the taped bus-bar and preventing smearing of the plasticpolyvinyl chloride adhesive tape; and,

FIG. 9 diagrammatically illustrates the several tank vats utilized in aconventional plating process, such as silver plating, wherein theplating rack is carrying a plurality of the bus-bars of the presentinvention from tank to tank in the plating procedures.

DESCRIPTION OF THE PREFERRED METHODS AND ARTICLE. EMBODIMENTS Referringto the drawings, and moreparticularly to FIG. 1 thereof, the referencenumeral 1 illustrates an electrical conductor, such as a bus-bar,commonly used in the fabrication of switchgear constructions. Referencemay be made to U.S. Pat. No. 3,444,131 1 for a typical bus-ductinstallation in equipment, such as used extensively in the electricalindustry.

It has been customary in the past to silver-plate busbars, or bus-ductsections, and to use, in this connection, considerable quantities of themetal silver in the plating solutions. The present invention isparticularly concerned with minimizing the quantity of silver used inthe plating of bus-bar connectors for certain applications. It is,consequently desirable, in employing the methods of the presentinvention, to provide a watertight preformed insulating sheath, orbooth," which is slipped over the copper or aluminum bus-bar and havingthe outer ends thereof sealed, in water-tight relation, to the bus-barsurface for preventing any corrosive solution liquids, in the platingsteps, from penetrating between the insulating tubing, or boot and thebus-bar surface during the plating process. In addition, it is desirableto eliminate liquid plating-solution dragout contamination by thebus-bar from tank to tank.

According to the present invention, it is proposed, as illustrated inFIG. 3, to tape spaced portions of the busbar 1 with a suitablethermoplastic resinous tape material, such as polyvinyl chlorideadhesive tape at locations A and B. As a subsequent operation, asillustrated in FIG. 4, the preformed thermoplastic insulating tubing 3is positioned, or pulled over the spaced taped portions A and B of thebus-bar l, and heat shrunk into place, at say, a temperature around300F. This provides a sealed watertight construction at the ends A," Bof the polyvinyl chloride tubing 3.

The excess tubing is then scalped, or trimmed to a specified dimension,as illustrated in FIG. 4A.

A second method of providing the desirable results of the presentinvention, and to eliminate the excess use of the metal silver in theplating solution steps, is to position the preformed thermoplastictubing material 3 over the bus-bar 1, as, for example, polyvinylchloride tubing, as illustrated in FIG. 5, and as a subsequent processstep, band or tape the ends of the preformed polyvinyl tubing 3 with asuitable thermoplastic resinous tape material 2, such as, preferably,polyvinyl chloride adhesive tape, such as illustrated in FIG. 7.

Pliofilm" a registered trademark is a rubber hydrochloride in the formof transparent sheets or rolls 0.001 inch thick. It is resistant tomoisture, water, oils, greases and most solvents; is heat scalable; andis very flexible. It is manufactured by the Goodyear Tire and RubberCompany and sold under the aforesaid trade name. it is a rubberderivative resembling resins.

The Polyvinyl chloride adhesive tape is supplied with a Pliofilm"backing attached to one side only. The use of Pliofilm as a backing overthe polyvinyl chloride tape enables it to be handled easily duringassembly, and prevents the polyvinyl chloride tape from smearing orphysically sticking to extraneous articles during the manufacturingsteps.

The thermoplastic insulating preformed tubing or boot" is a flexible,prestressed, heat reactive tubing and is supplied by the MinnesotaMining and Manufacturing Company under the trade name designation ofScotchtite 105C. The physical specifications of this tubing is coveredunder Westinghouse PDS 44791AG.

An alternate insulating preformed tubing or boot which is suitable forsatisfying the invention requirements is a thermoplastic boot or tubingmaterial supplied by Natvar Corporation, Woodbridge, N. J.

Although the invention has been previously described in connection withthe elimination of'the silver plating or undesired areas as a means ofeconomy; nevertheless where tin plating may be preferred as opposed tosilver plating, an economic advantage is still existant.

Plating tests, using the process steps described above, have proven theuse of polyvinyl chloride adhesive tape as a water-tight sealant onbus-bar ends la, lb between the insulating preformed tubing or boot 3and the bus-bar l is an efficient water-tight and chemicalsolutionsealant.

[t is to be clearly understood that the process steps of the presentinvention may be applicable to other electrical conductors requiringsimilar water-proofing, such as, for example, the sealing of plug-inopenings on thermoplastic insulated bus-bars.

Although the present invention has been concerned with the utilizationof thermoplastic boot, such as, for example, polyvinyl chloride resinousmaterial, and also the tape being of polyvinyl chloride resinousmaterial, nevertheless the invention has broader aspects, such as usingany insulation material having a sealed relation at its ends to theunderlying metal bus-bar surface. For example, instead of utilizing athermoplastic material, such as, for example, polyvinyl chlorideresinous material, a suitable thermosetting material, such as epoxyresin, or polyester resin may be used as a substitute. The essentialpoint of the invention is to provide a water-tight seal between theprefonned insulating boot" and the ends thereof, so that no liquidsolution, in the plating processes, may penetrate into the annular spaceprovided between the inside of the boot and the outer surface of theunderlying metal bus-bar.

FIG. 9 illustrates somewhat diagrammatically the many tanks, or vats,which are required in silver-plating aluminum or copper bus-bars, aswell known by those skilled in the art. For instance, in silver-platingan aluminum bus-bar, tank 1 would be a wash cleaning solution in hotwater, vat 2 would be a cold water rinse, vat 3 would be a nitric aciddip, followed by a cold water rinse. Then a vat would provide a zincatedip for say 45 seconds. This would be followed by a cold-water sprayrinse in another tank. This would be followed by a coldwater rinse. Thento provide a'copper coating over the previously applied zinc coating, acopper cyanide vat would provide a copper plating of say, for example,0.0003 inches for a 20 minute application. Then would follow a waterrinse, and then a tank providing a silver cyanide solution would be usedto plate a coating of, say 0.0001 inches silver on the previously coatedcopper coating. Another tank would reclaim the silver, and a finalhot-water rinse tank would be used, in which the silver-plated bus-barwould finally be clipped to test for blisters and accelerate drying.

In regard to silver plating a copper bus-bar, instead of an aluminumbus-bar, as previously described, again there would be many vats, ortanks utilized. For example, the cleaning steps; would consist of analkaline cleaning operation followed by water rinse, nitricsulfuric aciddip, water rinse, immersion silver plating, reclaim silver, and finallya hot water rinse to accelerate drying of the copper bus-bars. In anyevent, it is to be noted that several tanks, such as approaching twelvein number, are used in the successive dipping operations. If there werepenetration between the preformed boot" and the bus-bar, the liquidsolutions would tend to intermix by the carrying of the liquid solutionsby the bus-bar itself. This would not only be undesirable incontaminating the several vats, but, additionally, the corrosivesolutions would tend to deteriorate the metallic bus -bar portions underthe preformed boot.

Although there have been illustrated and described specific method stepsand bus-bar articles, it is to be clearly understood that the same weremerely for the purpose of illustration, and that plating changes andmodifications on the exposed electrical conductor ends may readily bemade therein by those skilled in the art, without departing from thespirit and scope of the invention.

We claim as our invention:

1. An elongated bus bar having an insulating sheath tubing ofthermoplastic resinous material disposed thereabout, both ends of theinsulating tubing being sealed in water-tight manner to the bareconductor surface of said elongated bus bar by insulating tape formed ofa thermoplastic resinous material, whereby liquid may not penetratebetween the inner bus bar and the outer sheath tubing.

2. An elongated bus bar having an insulating sheath tubing of polyvinylchloride disposed thereabout, both ends of the insulating tubing beingsealed in water-tight manner to the bare bus bar surface of saidelongated bus bar by polyvinyl chloride resinous tape, whereby liquidmay not penetrate between the inner bus bar and the outer sheath tubing.

3. The combination according to claim 2, wherein at least one of thetaped ends of the sheath tubing is covered with additional tape forhandling facility.

4. An elongated bus bar of appreciable length having an insulatingpreformed sheath tubing disposed thereabout and in physical contact withthe bare bus bar over a substantial portion of the length thereof,adhesive means comprising polyvinyl chloride resinous tape for sealingboth ends of the insulating preformed tubing in water-tight manner tothe bare bus bar surface, whereby liquid may not penetrate between theinner bus bar surface and the outer preformed sheath tubing in physicalcontact therewith.

5. The combination of claim 4, wherein the taped ends of the sheathtubing are covered with additional tape for handling facilities.

2. An elongated bus bar having an insulating sheath tubing of polyvinylchloride disposed thereabout, both ends of the insulating tubing beingsealed in water-tight manner to the bare bus bar surface of saidelongated bus bar by polyvinyl chloride resinous tape, whereby liquidmay not penetrate between the inner bus bar and the outer sheath tubing.3. The combination according to claim 2, wherein at least one of thetaped ends of the sheath tubing is covered with additional tape forhandling facility.
 4. An elongated bus bar of appreciable length havingan insulating preformed sheath tubing disposed thereabout and inphysical contact with the bare bus bar over a substantial portion of thelength thereof, adhesive means comprising polyvinyl chloride resinoustape for sealing both ends of the insulating preformed tubing inwater-tight manner to the bare bus bar surface, whereby liquid may notpenetrate between the inner bus bar surface and the outer preformedsheath tubing in physical contact therewith.
 5. The combination of claim4, wherein the taped ends of the sheath tubing are covered withadditional tape for handling facilities.